The sample holder is a component of an electron microscope providing the physical support for specimens under observation. Sample holders traditionally used for TEMs and STEMs, as well as some modern SEMs, consist of a rod that is comprised of three key regions: the end (300), the barrel (200) and the sample tip (100) (see, e.g., FIG. 1). In addition to supporting the specimen, the sample holder provides an interface between the inside of the instrument (i.e., a vacuum environment) and the outside world.
To use the sample holder, one or more samples are first placed on a support device. The support device is then mechanically fixed in place at the sample tip, and the sample holder is inserted into the electron microscope through a load-lock. During insertion, the sample holder is pushed into the electron microscope until it stops, which results in the sample tip of the sample holder being located in the column of the microscope. At this point, the barrel of the sample holder bridges the space between the inside of the microscope and the outside of the load lock, and the end of the sample holder is outside the microscope. To maintain an ultra-high vacuum environment inside the electron microscope, flexible o-rings are typically found along the barrel of the sample holder, and these o-rings seal against the microscope when the sample holder is inserted. The exact shape and size of the sample holder varies with the type and manufacturer of the electron microscope, but each holder contains these three key regions.
The sample holder can also be used to provide stimulus to the sample, and this stimulus can include temperature, electrical current, electrical voltage, mechanical strain, etc. One type of sample is a semiconductor device. The semiconductor device can be designed to have an array of electrical contact pads on it, and the sample holder can be designed to transfer electrical signals from an external source, through the holder, to the semiconductor device.
The need for high density arrays comes from an increasing demand to perform a wider variety of experiments on a sample within the microscope—a field known as in situ microscopy. As demonstrated in previous filings by the present inventors, semiconductor devices can be made to interact with a specimen positioned thereon by passing current or creating fields across or near a specimen. These electrical signals can be used to heat, cool, bias or charge a specimen, all while being viewed in real time within the microscope. Increasing the number of electrical contacts provided to a specimen increases the number of or type of experiments that can be done on the same device.
One type of sample holder is one in which (1) two semiconductor devices can be placed, (2) specimens can be placed on or near the semiconductor devices and (3) using the combination of holder and devices, the specimen's environment, including an electrical field and a gas or liquid flow, can be precisely controlled. Further, methods to introduce liquid or liquid mixtures to specimens within the microscope while containing and controlling the environment around specimens have been developed. However, there is a need for more advanced apparatuses and methods to contact and align devices used to form liquid or gas cells.